Question

我的应用程序无法正常运行，运行程序时显示0.00。如何格式化代码或添加更多元素以使其实际访问网页？我在Manifest文件中有访问代码，而我的strings.xml和activity_main.xml似乎没有给出任何麻烦。我主要想知道我是否真正理解了应用程序访问互联网的java文件中的所有组件。

我的代码段：

public class MainActivity extends Activity {
    private static final String DEBUG_TAG = "HttpExample";
    private EditText urlText;
    private TextView textView;
    private Editable stock_symbol;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);   
        urlText = (EditText) findViewById(R.id.et1);
        stock_symbol = urlText.getText();
        textView = (TextView) findViewById(R.id.tv1);
    }
    public void myClickHandler(View view) {
        // Gets URL from UI's text field.
        String stringUrl = urlText.getText().toString();
        ConnectivityManager connMgr = (ConnectivityManager) 
            getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo networkInfo = connMgr.getActiveNetworkInfo();
        if (networkInfo != null && networkInfo.isConnected()) {
            new DownloadWebpageText().execute(stringUrl);
        } else {
            textView.setText("No network connection available.");
        }
    }

     /*Uses AsyncTask to create a task away from the main UI thread. This task takes a 
      * URL string and uses it to create an HttpUrlConnection. Once the connection
      * has been established, the AsyncTask downloads the contents of the webpage as
      * an InputStream. Finally, the InputStream is converted into a string, which is
      * displayed in the UI by the AsyncTask's onPostExecute method.*/
     private class DownloadWebpageText extends AsyncTask <String, Void, String>{
        @Override
        protected String doInBackground(String... urls) {
            // params comes from the execute() call: params[0] is the url.
            try {
                return downloadUrl(urls[0]);
            } catch (IOException e) {
                return "Unable to retrieve web page. URL may be invalid.";
            }
        }
        @Override
        protected void onPostExecute(String result) {
            String symbol = result.substring(result.indexOf('>') + 1, result.lastIndexOf('<'));
            textView.setText(symbol);
       }
     // Given a URL, establishes an HttpUrlConnection and retrieves
     // the web page content as a InputStream, which it returns as
     // a string.
     private String downloadUrl(String myurl) throws IOException {
         InputStream is = null;
         // Only display the first 500 characters of the retrieved web page content.
         int len = 500;
         try {
             URL url = new URL("http://finance.yahoo.com/d/quotes.csv?s=" + stock_symbol + "&f=k1");
             HttpURLConnection conn = (HttpURLConnection) url.openConnection();
             conn.setReadTimeout(10000 /* milliseconds */);
             conn.setConnectTimeout(15000 /* milliseconds */);
             conn.setRequestMethod("GET");
             conn.setDoInput(true);
             // Starts the query
             conn.connect();
             int response = conn.getResponseCode();
             Log.d(DEBUG_TAG, "The response is: " + response);
             is = conn.getInputStream();

             // Convert the InputStream into a string
             String contentAsString = readIt(is, len);
             return contentAsString;

         // Confirms InputStream is closed after the app is finished using it.
         } finally {
             if (is != null) {
                 is.close();
             } 
         }
     }
     // Reads an InputStream and converts it to a String.
     public String readIt(InputStream stream, int len) throws IOException, UnsupportedEncodingException {
         Reader reader = null;
         reader = new InputStreamReader(stream, "UTF-8");        
         char[] buffer = new char[len];
         reader.read(buffer);
         return new String(buffer);
     }
    }
}

Answer 1

 public String readIt(InputStream stream, int len) throws IOException, UnsupportedEncodingException {
         Reader reader = null;
         reader = new InputStreamReader(stream, "UTF-8");        
         char[] buffer = new char[len];
         reader.read(buffer);
         return new String(buffer);
     }

只读取输入流的len个字节。

使用Apache Commons IO库直接将InputStream转换为String：

 public String readIt(InputStream stream, int len) throws IOException, UnsupportedEncodingException {
     return IOUtils.toString(stream, "UTF-8");
 }

根据用户输入的股票代码显示股票的应用程序

1 个答案: